A drench with a solution of neem oil and an emulsifier and RO water, in the ratio of 1:100 maximum: 10ml neem oil to 990ml RO water for 1 litre of solution.
Well, you can use Neem oil to get rid of them. You can also use Beauveria, which will actually attack the root aphids.
There are also hydrogen peroxide mixes you can use to saturated your soil with and destroy all the little buggers.